Find a linear operator $T: \mathbb C^2 \to \mathbb C^2$ such that $$\|T\| > \sup_{\|f\| \leq 1} \left|\langle Tf, f \rangle\right|,$$ where $\langle \cdot, \cdot \rangle$ is the standard inner product.
I know that $$\|T\| := \sup_{f \neq 0} \frac{\|Tf\|}{\|f\|} = \sup_{\|f\|=1} \|Tf\| = \sup_{\|f\|\leq 1} \|Tf\|.$$ This does not seem to be helpful. Any help, please? Thank you!
Hint: what happens if $T$ is a rotation?